Method for treating packaging material with a hydrocolloid release coating



United States Patent Oflice 3,519,470 Patented July 7, 1970 3,519,470METHOD FOR TREATING PACKAGING MATERIAL WITH A HYDROCOLLOID RELEASECOATING Arthur L. Gordon, Des Plaines, and Leonard A. Warwick, Niles,Ill., assiguors to Kraftco Corporation, New York, N.Y., a corporation ofDelaware No Drawing. Filed July 10, 1967, Ser. No. 652,041 Int. Cl. B44d5/08 US. Cl. 117-86 11 Claims ABSTRACT OF THE DISCLOSURE A release agentfor packaging materials to be used with food products and a method forproviding improved release properties for such packaging materials. Therelease agent is a thin film or layer of a suitable hydrocolloid.Suitable hydrocolloids may be selected from treated or untreatedstarches, polysaccharide gums, farinaceous materials or modifiedcellulose materials.

The present invention relates generally to packaging material and moreparticularly relates to packaging materials for use in packaging foods,with improved release properties.

-It is desirable to wrap certain foods in a packaging material prior todistribution. However, various of these foods, such as some types ofcheese, margarine, or some types of candy, tend to stick or cling to thepackaging material when the consumer attempts to remove the packagingmaterial piror to consumption. Such sticking or clinging is undesirablein that it may lead to food wastage or tearing of the packagingmaterial.

Various materials have been used on the interior surface of packagingmaterials to prevent blocking. Blocking is defined as undesired adhesionbetween touching layers of a packaging material such as occurs undermoderate pressure conditions which occur during storing or wrappingoperations. For example, it is known to provide a thin coating of drygranular starch on the packaging material. Such coating of dry granularstarch, however, is not satisfactory in effecting release of thepackaging material from the food product that is wrapped therein.

Accordingly, it is an object of the present invention to provide animproved packaging material. It is another object of the presentinvention to provide a packaging material with improved releaseproperties when used for food products. It is a further object of thepresent invention to provide a method for treating packaging materialswhich provides easy release of the packaging material from the foodproducts at the time of consuming.

These and other objects of the present invention will become more clearfrom the following detailed disclosure.

In general, in accordance with certain features of the presentinvention, packaging materials which are used to package food productsare coated with a hydrocolloid which forms a thin film on the interiorsurface of the packaging material. As used herein, the term hydrocolloidrefers to any of several substances which may be hydrated with Water toyield gels and which will subsequently form thin films upon drying of athin coating of the hydrated hydrocolloid. In particular such classes ofhydrocolloids as treated or untreated starches, polysaccharide gums,farinaceous flours, and modified cellulose materials are suitable forthe practice of the present invention. For example, cornstarch, wheatflour, guar gum, carrageenan and carboxy methyl cellulose andcombinations of these materials are suitable for the practice of thepresent invention.

In accordance with the present invention the hydrocolloid may first bemixed with cold water to form a paste or suspension. The suspension isthen heated to a predeterimned elevated temperature to promote hydrationof the hydrocolloid. The suspension is maintained at the elevatedtemperature under stirring conditions until the hydration is completedand a colloidal solution or gel is formed. The hydrocolloid gel is thenapplied to the packaging materials by any suitable technique. Forexample, a Gravure cylinder and knife combination may be used to apply acontrolled thin film layer of the hydrocolloid to a continuous Web ofpackaging material.

The hydrocolloid material is added to Water at a level so as to providea suitable viscosity at the temperature of application to the Web ofpackaging material. For example, when the hydrocolloid material iscornstarch, the cornstarch is added so as to provide from about 3percent to about 10 percent by weight of cornstarch in water. Suitablelevels of other hydrocolloids or mixtures of hydrocolloids are readilydetermined by one skilled in the art. These levels are, in general, fromabout 2 percent to about 12 percent by weight.

After the hydrocolloid suspension has been hydrated by heating, it isheld at a temperature so as to provide the desired viscosity forapplication to the packaging ma terial. In general, this temperaturewill be from about 15 to about 35 F. below the boiling point of thehydrocolloid-Water mixture.

After application to the packaging material the hydrated hydrocolloid isdried so as to form a thin con tinuous film on the packaging material.This hydrocolloid film is subsequently placed in contact with the foodproduct during the Wrapping operation so as to provide improved releaseproperties.

Certain readily hydrated hydrocolloid materials such as pre-gelatinizedstarch, which may be derived from any suitable food source such as rice,potato or tapioca, dextrin, and nonionic water soluble cellulose ethersmay be applied to the surface of the packaging material in asubstantially dry condition.

It is believed that these readily hydrated hydrocolloid materials havethe ability to hydrate so as to form a thin film in situ by absorptionof moisture from the packaged product. Application of these readilyhydrated hydrocolloid materials to the packaging material may beeffected by any suitable method. One such method is simply dusting ofthe hydrocolloid material onto the surface of the packaging material.Another method is to provide a slurry of the hydrocolloid material in asuitably inert organic carrier, such as isopropanol of ethanol. Thehydrocolloid slurry may then be applied to the surface of the packagingmaterial and the organic carrier removed by drying so as to provide athin, dry layer of the hydrocolloid material.

The thin, dry film of readily hydrated hydrocolloid material issubsequently placed in contact with the food product during the wrappingopeartion. The thin, dry layer of hydrocolloid material absorbs moisturefrom the packaged food product so as to form a thin substantiallycontinuous film with improved release properties.

The hydrocolloid, whether hydrated by heating of a slurry of thehydrocolloid or whether applied in a substantially dry condition, isapplied to the packaging material so as to provide a level of from about0.5 to about 5.0 lbs. of the hydrocolloid (dry basis) per ream ofpackaging material. For purposes of this application a ream refers to anarea of 3,000 square feet. At levels above about 5.0 lbs./ ream nosubstantial additional benefit is derived and the total cost of thehydrocolloid material used is consequently greater. However, levelsabove about 5.0 lbs/ream may sometimes be used to achieve 3 improvedmachining and handling properties for the coated packaging material.

The packaging material of the present invention is particularly suitablefor wrapping process cheese and certain details are hereinafterdescribed with particular reference to process cheese. However, itshould be understood that the packaging material is equally suitable forwrapping other food products which have a tendency to stick or adhere tothe packaging material. Such food products include cream cheese,margarine, caramels, or toffee. When process cheese is being packaged inaccordance with the present invention it is preferred to select arelease agent that provides a dull, translucent film rather than onewhich provides a glossy, shiny finish to the packaging material.Particularly preferred release agents for packaging process cheese arepre-gelatinized and non-gelatinized starch and carrageenan. In apreferred embodiment of the present invention, a mixture of cornstarchand carrageenan is used as the release agent. The cornstarch andcarrageenan are present in the mixture at a ratio of from about 1:1 toabout 5:1 parts of cornstarch to carrageenan.

Process cheese in general is made by grinding and mixing together byheating and stirring one or more cheeses of the same or of two or morevarieties, together with other ingredients, until a homogeneous plasticmass is formed. American Cheddar cheese and other American-type cheesessuch as Colby, and also Swiss, Gruyere, Brick, Limburger and othercheeses are examples of cheeses which are used in the production ofprocess cheese.

The cheese for each batch is cleaned and cut into uniform size if thecheese pieces are large. The cheese pieces are then passed through agrinder into a steamjacketed kettle or a horizontal cooker. The otheringredients, such as emulsifiers and flavoring materials, are addedeither as the cheese is run through the grinder or while it is beingheated. The cheese is heated and is held at an elevated temperature forat least 30 seconds. When the cheese is smooth, homogeneous, glossy andcreamy it is automatically packaged into cartons while in a heated fluidcondition. The cartons are lined with a packaging material which may besealed to exclude air. The packaged cheese is then cooled to roomtemperature and is placed under refrigeration. The high temperatureattained in heating, together with the heat retained during the timerequired to cool the cheese to room temperature makes the cheesepractically sterile, and the cheese keeps well and does not ripenfurther. However, the cheese tends to adhere to the packaging materialand subsequent removal of the packaging material is difiicult.

Any suitable packaging material which is commonly used for packagingfood products that tend to adhere to the packaging material may be usedin accordance with the present invention. One such commonly usedpackaging material for use in packaging cheese is a cellophane/ aluminumfoil/ fortified wax lamination. Fortified wax refers to well-knownwax-resin blends, wherein the resin is a polymer selected to providedesired viscosity or body.

The following examples further illustrate various features of thepresent invention but are intended to in no way limit the scope of theinvention which is defined in the appended claims.

EXAMPLE I Dry cornstarch was added at a level of 5.7 weight percent towater which had been heated to F. The mixture was stirred vigorously forfive minutes until the starch was uniformly dispersed in the water. Thestarch mixture was then gradually heated over a period of about 30minutes to a boil (212 F.) under conditions of mild agitation. Thestarch mixture was held at a boil for 1 /2 minutes to fully gelatinizethe starch. Heating was then stopped and the mixture was then cooledrapidly in less than one minute to 190 F. and held at that temperatureuntil used.

The starch mixture was then applied to a web of cellophane/aluminumfoil/fortified wax laminate packaging material. The starch mixture wasapplied with a Gravure cylinder and knife combination so as to providestarch at a level of one pound per ream of packaging material (drybasis). The coated packaging material was then dried to provide a thinfilm of dry starch adjacent to the fortified wax layer. The packagingmaterial was then cut and folded to provide an open-mouthed rectangularpackage with a flap that could subsequently be folded over to seal themouth. The package was folded to place the starch film on the interiorsurface of the package. Process cheese was then introduced into thepackage at a temperature of F. to provide a two pound block of processcheese. The packages were then sealed.

Process cheese at a temperature of 165 F. was also packaged in a similarmanner into cellophane/aluminum foil/fortified wax packaging materialwhich had not been treated to provide a thin film of starch. Thepackaging material was, however, treated in accordance with knownprocedures to prevent blocking of the packaging material by providing athin coating of dry, granular, non-gelatinized starch on the fortifiedwax surface. Such coating of dry starch is known to prevent blocking ofpackaging materials. The coating of dry starch was applied b sprayingthe fortified wax surface of the packaging material with a 60 weightpercent starch slurry in alcohol so as to provide a level of 5 pounds ofdry granular starch per ream of packaging material. This packagingmaterial was then dried, leaving a coating of dry granular starch on thefortified wax surface. The process cheese which had been packaged inaccordance with the present invention and the process cheese which hadbeen packaged with a coating of dry granular starch were compared aftervarious periods of storage at temperatures of 72 F. and 45 F. todetermine the release properties. The release propertis were visuallynoted by observing and rating the amount of cheese which adhered to thewrapper after a specified period of storage. After each two poundpackage of proc ess cheese was unwrapped the condition of the wrapperwas observed and noted according to the following schedule:

( 1) Clean (no sign of cheese adherence to the packaging material).

(2) Very slight to clean.

(3) Very slight.

4 Slight.

(5) Slight to moderate.

(6) Moderate.

(7) Moderate to definite.

(8) Definite (definite signs of cheese adherence to the packagingmaterial).

The data collected according to the above schedule was used to preparethe following table:

TAB LE 1 Average grading of packing material at given examinationperiods and storage conditions Initial 1 month 2 months 3 months 4months 5 months Release coating material 45 72 45 72 45 72 45 72 45 7245 72 Starchfilm 1. 5 1.5 1.5 1.5 1.5 1. 5 1. 5 1.0 1.0 1.0 1.0 1.0 Drygranular starch (control) 7. 5 6. 0 7. 0 5. 0 7. 0 4. 5 7. 0 4. 0 7. 04. O 7. 0 3. 0

The data for the above Table 1 was obtained by unwrapping sixteen twopound blocks of process cheese at the intervals noted and visuallygrading the appearance of each of the packaging materials. The averageof the grades was then recorded in Table 1. As can be seen from theabove grading scale, the lower the average grade the better the releaseproperties of the packaging material.

It can readily be seen that packaging material treated in accordancewith the present invention to provide a thin film of release agentmaterial adjacent the surface of the processed cheese is superior to theknown method of applying a dry starch coating.

EXAMPLE II A cellophane/ aluminum foil/ fortified wax packaging materialwas coated with a 5.7 weight percent mixture of starch and carrageenanwhich had been hydrated in accordance with the method of Example I. Themixture was applied to the packaging material at a temperature of 185 F.The ratio of starch to carrageenan was 4 to 1 on a weight basis. Processcheese was packaged in the packaging material coated with thestarch-carrageenan mixture and was then compared with the process cheesewhich had been packaged in packaging materials which had been coatedwith dry granular starch in a manner as heretofore described. The datafrom the above investigation was then used to prepare Table 2.

TAB LE 2 The starch slurry at a temperature of 70 F. was applied to thepackaging material by means of a Gravure cylinder. The starch slurry wasapplied at a rate sufficient to provide 3 pounds of starch per ream ofpackaging material (dry basis). The coated packaging material was thenpassed through a ten foot long drying tunnel maintained at a temperatureof 200 F. at a rate of 100 feet per minute to evaporate the isopropanol.

The coated packaging material was then used to package process cheese.After 90 days storage, the release properties of the packaging materialprepared in accord ance with the above procedure were still excellent.

EXAMPLE V A cellophane/aluminum foil/fortified wax packaging materialwas coated with a mixture of pre-gelatinized starch and a nonionic watersoluble cellulose ether. One hundred pounds of a slurry containing amixture of readily hydrated hydrocolloids in an inert organic carrierwas prepared. The slurry contained 5 weight percent of pre-gelatinizedstarch and 8 weight percent of nonionic water soluble cellulose ether.Isopropanol was used as the inert organic carrier. The slurry wasapplied to the packaging material by means of a Gravure cylinder so asto provide 0.8 pound of the hydrocolloid mixture (dry basis) per ream ofthe packaging material. The coated packaging material was then passedthrough a ten foot Average grading of packing material at givenexamination periods and storage conditions Initial 1 month 2 months 3months 4 months 5 months Release coating material 45 72 45 72 45 72 4572 45 72 45 72 Carageenan/Starch film l. 5 1. 5 1. 5 1. 5 1. 5 1. 5 5 1.0 1. 0 1. 0 1. 0 1. 0 Dry granular starch (control) 7. 0 6. 0 7. 0 5. 57. 0 4. 5 7. 0 4. 0 7. 0 4. 0 7. 0 3. 0

From the above it can readily be seen that the packaging material of thepresent invention which had a hydrated starch-carrageenan film issuperior.

EXAMPLE III Various other hydrocolloid mixtures were used to coatcellophane/aluminum foil/fortified wax packaging materials in accordancewith the present invention. Data in connection with the releaseproperties of these hydrocolloid materials are presented below in Table3.

TABLE 3 Average grading of packing material at given examination periodsand storage conditions Initial lmonth 2m0nths 3months 4menths 5monthsRelease coating Weight material percent 45 72 45 72 45 72 45 72 45 72 4572 CMC 20 SGmrch g8}1.5 2.0 1.0 1.5 1.0 2.0 1.0 1.5 2.0 3.0 1.0 3.0

uar gum. $3 g8}6.5 7.5 6.0 7.0 6.0 7.0 6.0 7.0 6.0 7.0 6.0 8.0

eat our Starch }1.5 2.0 1.0 4.5 1.0 5.0 1.0 1.0 2.0 5.0 2.0 8.0 Drygranular starch (control) 100 8.0 8.0 8.0 8.0 8. 8.0 8.0 8.0 8.0 8.0 8.08.0

From the above, it can be seen that various mixtures of hydrocolloidsmay be used in the practice of the present invention. Certain releasecoating materials are particularly effective in preventing sticking whenthe food product is stored at relatively low temperatures, while othersare more suitable for relatively high temperature storage, such as atroom temperature. A suitable hydrocolloid or mixture of hydrocolloidsfor particular conditions of storage is readily determined by oneskilled in the art.

EXAMPLE IV A cellophane/aluminum foil/fortified wax packaging materialwas coated with dry, pre-gelatinized starch in accordance with thefollowing procedure. Sixty pounds of pre-gelatinized starch was added to48 pounds of 99 weight percent isopropanol. The starch-isopropanolmixterials which are to be used for packaging food products to provide arelease coating thereon which method comprises dispersing a film forminghydrocolloid or mixture of hydrocolloids in an aqueous medium, heatingsaid dispersion of film forming hydrocolloid or mixture of hydrocolloidsto a predetermined temperature for a time sufficient to hydrate saidhydrocolloid or mixture of hydrocolloids and increase the viscosity to apredetermined level, maintaining said dispersion at an elevatedtemperature, applying said hydrocolloid or mixture of hydrocolloids in athin coating to the surface of the packaging material, and drying saidthin coating of viscous hydrocolloid or mixture of hydrocolloids so asto provide a thin film of hydrated hydrocolloid or mixture of hydratedhydrocolloids, said viscous hydrocolloid mixture being applied at alevel sufficient to provide from about 0.5 to about ture was agitated soas to provide a uniform starch slurry. 5.0 pounds of said hydratedhydrocolloid or said mixture of hydrated hydrocolloids on a dry basisper ream of packaging material.

2. The method of claim 1 wherein said surface of the packaging materialis a fortified wax.

3. The method of claim 1 wherein said hydrocolloid or mixture ofhydrocolloids is selected from the group consisting of treated oruntreated starch, polysaccharide gums, farinaceous flours,carboxymethylcellulose and combinations thereof.

4. The method of claim is guar gum.

5. The method of claim is carrageenan.

6. The method of claim is wheat flour.

7. The method of claim is carboxymethyl cellulose.

8. The method of claim 1 wherein said hydrocolloid is a mixture ofcornstarch and carrageenan, said cornstarch being present at a ratio offrom about 1:1 to about 5:1 by weight with respect to said carrageenan.

9. The method of claim 1 wherein said hydrocolloid is cornstarch.

10. The method of claim 1 wherein the hydrocolloid or mixture ofhydrocolloids is dispersed in said aqueous 1 wherein said hydrocolloid 1wherein said hydrocolloid 1 wherein said hydrocolloid 1 wherein saidhydrocolloid 8 medium at a level of from about 2 percent to about 12percent by weight.

11. The method of claim 1 wherein the dispersion of a hydrocolloid ormixture of hydrocolloids is maintained at an elevated temperature offrom about 15 F. to about 35 F. below the boiling point of thedispersion.

References Cited UNITED STATES PATENTS 20 WILLIAM D. MARTIN, PrimaryExaminer R. HUSACK, Assistant Examiner US. Cl. X.R.

